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Sunday, October 4, 2015

Nanodiamonds

Nanodiamonds are tiny crystals only a few nanometers in size. While they possess the crystalline structure of diamonds, their properties diverge considerably from those of their big brothers because their surfaces play a dominant role in comparison to their extremely small volumes.

Suspended in aqueous solutions, they could function as taxis for active substances in biomedical applications, or be used as catalysts for splitting water.

Researchers have, for the first time, levitated individual nanodiamonds in vacuum. Nanodiamonds trapped at atmospheric pressure are continuously agitated by collisions with the air molecules around them. Trapping the diamonds in vacuum removes the effect of all these air molecules.

"This allows us to exert mechanical control over them," said Levi Neukirch, lead author of the paper.

"They turn into little harmonic oscillators."

One of the most promising ways to capture, generate and manipulate photons is with nanodiamonds. The secret is to create nanodiamonds with a defect in their structure where a nitrogen atom has taken the place of a carbon.

Quantum physicists are interested in these so-called nitrogen vacancies because they can capture, store and emit the quantum information that photons carry. What’s more, they do all this at room temperature. It is even possible to manipulate this information using magnetic and electric fields.

According to a study featured in Nature Nanotechnology, the possible uses of nanodiamonds are endless. Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. They are also non-toxic, which makes them well suited to biomedical applications. “These little gems have a wide range of potential applications in tribology, drug delivery, bioimaging and tissue engineering, and also as protein mimics and a filler material for nanocomposites”.

Nanodiamonds have been used as catalysts in scientific experiments, seeding material for cultivating diamond films, additives for automobile oils, galvanic coatings and polishing compounds.

Nanodiamonds have made the most headlines for their potential use in fighting cancer.

Nanodiamonds could be the solution for dealing with chemoresistant cancer stem cells, according to a study published in ACS Nano. A team of researchers has repurposed existing chemotherapy drugs into effective agents against chemoresistant cancer stem cells with nanotechnology.

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Sediments found beneath the floor of Lake Cuitzeo in central Mexico support theories of a major cosmic impact event 12,900 years ago. A 13,000-year-old layer of sediment contains materials associated with impact events, such as soot, impact spherules and nanodiamonds.

The nanodiamonds found at Lake Cuitzeo are of a variety known as lonsdaleite, even harder than “regular” diamond and only found naturally as the result of impact events.

It’s thought that a large asteroid or comet entered Earth’s atmosphere at a shallow angle 12,900 years ago, melting rocks and causing widespread destruction. This event would have occurred just before a period of unusually cold climate known as the Younger Dryas.

The only other widespread sedimentary layer ever found to contain such an abundance of nanodiamonds is found at the K-T boundary, 65 million years ago. This corresponds to the impact event that led to the extinction of the dinosaurs.